Limbaugh accused O'Reilly of marginalizing his owner viewers — opponents of gay marriage — by saying that they didn't have a compelling argument and calling them "Bible thumpers."

"Well. So how many of you who watch Fox are Bible thumpers?" Limbaugh said after playing a clip of O'Reilly's comments on the subject.

"Do you think there are any Bible thumpers, quote/unquote, that watch Fox? Because last night you were sort of marginalized on The Factor as not having a compelling argument and just being a bunch of Bible thumpers."

On Tuesday, O'Reilly agreed with guest Megyn Kelly and said that the "compelling argument is on the side of homosexuals." He did not endorse gay marriage, but he said he did not feel strongly about it one way or another.

"That's where the compelling argument is," O'Reilly said. "We're Americans. We just want to be treated like everybody else.

"That's a compelling argument. And to deny that, you've got to have a very strong argument on the other side. And the other side hasn't been able to do anything but thump the Bible."

The Supreme Court heard oral arguments this week on two high-profile same-sex marriage cases — California's Proposition 8 law and the federal Defense of Marriage Act.